Command for Big Omega [duplicate]

Question

Possible Duplicate:
How to look up a math symbol?

How can I the code for "big omega", NOT \omega which is little omega. I want the symbol that's used in big-O notation.

Answer 1

It's quite easy: \Omega. Also the other big letters just begin with a capital letter, e.g. \Delta, \Pi. I can also recommend DeTeXify, there you can draw something with your mouse, and and engine tries to recognize what you drew and presents some suggestions.

Answer 2

Perhaps you are looking for something like this:

\documentclass{article}
\usepackage{amsmath}
\newcommand{\BigO}[1]{\ensuremath{\operatorname{O}\bigl(#1\bigr)}}
\begin{document}
The symbol for Big-O notation:
\BigO{n}
\end{document}

If you want the brackets to resize automatically you can use:

\newcommand{\BigO}[1]{\ensuremath{\operatorname{O}\left(#1\right)}}

Answer 3

Add

\newcommand{\bigO}{\ensuremath{\mathcal{O}}}% big-O notation/symbol

to your document (preamble) and then you can use \bigO. If you want to use \Omega instead to represent your biig-O notation, then add

\newcommand{\bigO}{\ensuremath{\Omega}}% big-O notation/symbol

instead.

Answer 4

An up-front comment (not directly an answer, but I'll get to that soon): The Greek "little" o, or omicron (as opposed to the "big" o, i.e., omega), is identical in appearance -- in both its lowercase and uppercase versions -- to the Roman lowercase letters "o" and "O". Hence there are no TeX commands for $\omicron$ and $\Omicron$.

To denote the asymptotic order of magnitudes "little-oh" and "big-Oh", respectively, I've frequently encountered $o$ and $O$ (i.e., using TeX's math-italics font) and -- for big-Oh only -- $\mathcal{O}$. Most math fonts (including Computer/Latin Modern) do not have lowercase mathcal letters, therefore one generally does not see $\mathcal{o}$ for "little-oh".

Incidentally, the mtpro2 package -- when loaded with the mtpcal option -- does have a symbol for $\mathcal{o}$. Unfortunately, the package is not free, but its cost (for noncommercial licenses) is very reasonable. The first line in the image below shows the results of $o$ and $O$, and the second line shows the results of $\mathcal{o}$ and $\mathcal{O}$ commands produced with the mtpro2 package loaded.

Finally, I must confess that I have not yet seen the symbol $\Omega$ (uppercase-Omega) used in asymptotic "big-Oh" notation, but that may be just be a consequence of my lack of erudition.